1. Field of the Invention
The present invention relates to a substrate gripper device for gripping a substrate such as a semiconductor substrate, a glass substrate, a liquid-crystal panel, or the like which needs to be highly clean while the substrate is being cleaned or spin-dried.
2. Description of the Prior Art
As semiconductor devices become more highly integrated in recent years, line-widths of circuit interconnections become thinner and the distances between those interconnections also become smaller. While in various fabrication processes, fine semiconductor particles, dust particles, and peeled-off pieces such as crystalline bodies tend to be attached to semiconductor substrates. If foreign matter particles which is greater than the distance between interconnections existed on a semiconductor substrate, then a short circuit would be caused between the interconnections. Therefore, all foreign matter particles on semiconductor substrates have to be removed to avoid undesirable short circuits.
Such unwanted foreign matter particles also have to be removed from substrates with fine patterns thereon including glass substrates for use as masks and liquid-crystal panels during fabrication processes thereof. To meet the above requirements, there has been desired a cleaning technique for washing away fine foreign matter particles of submicron sizes from substrates such as semiconductor substrates.
While those substrates are being cleaned or subsequently spin-dried, they have to be reliably gripped by a substrate gripper device.
It has been widely practiced to rotate a substrate at high speeds ranging from 2000 to 3000 rpm while it is being gripped by a substrate gripper device for cleaning or spin-drying the substrate.
One conventional substrate gripper device is shown in FIG. 1 of the accompanying drawings. As shown in FIG. 1, a plurality of support pins 2 are vertically mounted on a peripheral edge of a disk-shaped turntable (substrate stage) 1 which is rotatable at high speeds, and a substantially circular semiconductor substrate S is placed on and held by respective shoulders 3 of the support pins 2. The substrate gripper device is disclosed in Japanese laid-open patent publication No. 4-53684, for example.
One problem with this substrate gripper device is that when the turntable 1 with the semiconductor substrate S supported thereon rotates at high speeds, the semiconductor substrate S is liable to lift off from the support pins 2, and the substrate gripper device is incapable of reliably preventing the semiconductor substrate S from being lifted off from the support pins 2.
FIG. 2 shows another known substrate gripper device disclosed in Japanese laid-open patent publication No. 3-30426, for example. As shown in FIG. 1, a circumferential edge of a semiconductor substrate S is gripped in place between upper surfaces of plural arms 4 extending radially outwardly and presser fingers 6 that are normally urged downwardly by respective springs 5. For releasing the semiconductor substrate S, the substrate gripper device needs a mechanism for turning the pressing fingers 6 in an opening direction or lifting the pressing fingers 6 off the semiconductor substrate S. Since such a mechanism has to rotate with the semiconductor substrate S, it is considerably complex in structure. The entire assembly that rotates is relatively heavy, and cannot rotate at speeds beyond a certain speed limit.